Who is Skelly from The Graduation of Jake Moon and what is their importance?

Skelly is Jake's grandfather. He is the only father Jake has ever known, and because of the man he is..... Jake loves and respects him completely. Over the course of the novel, Skelly begins developing the early signs of Alzheimers, which gets progressively worse with each chapter. Jake finds it difficult to watch the changes in his grandfather but responds with the love and kindness Skelly instilled in him.